Chemical looping steam reforming for hydrogen production from waste cooking oil was investigated using a packed bed reactor. The steam to carbon ratio of 4 and temperatures between 600 and 700 °C yielded the best results of the range of conditions tested. Six cycles at two weighted hourly space velocities (WHSV of 2.64 and 5.28 hr -1 ) yielded high (>0.74) and low (<0.2) oil conversion fractions respectively, representing low and high coking conditions. The WHSV of 2.64 hr -1 yielded product concentrations closest to equilibrium values calculated assuming a fresh rapeseed oil composition. Repeated cycling revealed some output oscillations in reactant conversion and in the extent of Ni-NiO conversion, but did not exhibit deterioration by the 6 th cycle. The selectivity of CO, CO 2 and CH 4 were remarkably constant over the performed cycles, resulting in a repeatable syngas composition with H 2 selectivity very close to the optimum.

Pimenidou, P, Rickett, G, Dupont, V and Twigg, MV (2010) AbstractHigh purity hydrogen (>95%) was produced at 600 °C and 1 atm by steam reforming of waste cooking oil at a molar steam to carbon ratio of 4 using chemical looping, a process that features redox cycles of a Ni catalyst with the in-situ carbonation / calcination of a CO 2 -sorbent (dolomite) in a packed bed reactor under alternated feedstreams of fuel-steam and air. The fuel and steam conversion were higher with the sorbent present than without it. Initially, the dolomite carbonation was very efficient (100 %), and 98 % purity hydrogen was produced, but the carbonation decreased to around 56% with a purity of 95% respectively in the following cycles.Reduction of the nickel catalyst occurred alongside steam reforming, water gas shift and carbonation, with H 2 produced continuously under fuel-steam feeds. Catalyst and CO 2 -sorbent regeneration was observed, and long periods of autothermal operation within each cycle were demonstrated.

Ultimate and proximate analyses and thermal degradation of bio oils from pinewood and palm empty fruit bunches (PEFB) were carried out to evaluate the oils' potential for production of fuels for transport, heat and power generation, and of hydrogen via the calculation of performance indicators. The pinewood and PEFB oils indicated good theoretical hydrogen yields of 13.7 and 15.9 wt% via steam reforming, but their hydrogen to carbon effective ratios were close to zero, and their propensity for fouling and slagging heat exchanger surfaces via combustion was high. Both oils exhibited two phases during mass loss under nitrogen flow at heating rates of 3-9 K min -1 , but the kinetics of their thermal degradation from TGA-FTIR analysis indicated different degradation mechanisms that were well reproduced by a n th order reaction model for pinewood and Jander's 3D-diffusion model for PEFB. These findings lead to recommendations on pretreatments prior to the oils' utilisation.

The non-isothermal kinetic and thermal behaviour of a naturally formed dolomite in conditions that approach in situ CO2 capture in chemical looping reforming, were investigated. The performance of this dolomite was studied at micro-scale in 'dry' conditions, as well as at macro-scale in 'dry' and 'wet' conditions to investigate the effects of scale (3 mg, 2.5 g), partial pressures of CO 2 (< 15 kPa) and steam, and deactivation upon limited cycling. The carbonation and calcination kinetics were modelled using an improved iterative Coats-Redfern method. Increasing CO 2 partial pressures on the 'dry' macroscale exacerbated the experimental carbonation conversions in an inversely proportional trend when compared with those at micro-scale. The presence of steam had a positive effect on CO 2 chemisorption. Steam had a negligible influence on the calcination activation energies. The activation energies of carbonation were increased for the experiments at the highest CO 2 partial pressures under wet conditions.

In this work, the effect of the nanosized CZA2 (cerium-zirconium-aluminium) on the performance and emissions in a two-cylinder indirect injection (IDI) diesel engine, was studied. CZA2 was dispersed in diesel (D100) and waste cooking oil and tallow origin biodiesel-diesel blends (B10, B20, B30) and tested at different engine loads and constant speed. The nanocatalyst (CZA2) increased the brake specific fuel consumption (BSFC) and decreased the brake thermal efficiency (BTE, %) of all tested fuels, at all loads, except B20 at the lowest load. CZA2 reduced nitrogen oxides (NOx) from D100 at low and high engine loads, as well as carbon monoxide (CO) and unburned hydrocarbons (HC) at medium and high tested loads. The dispersion of CZA2 promoted the combustion of the biodiesel blends by almost eliminating HC while reducing NOx and CO emissions at various loads. Thermogravimetric analysis (TGA) coupled with Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy revealed that the addition of CZA2 in diesel and biodiesel under pyrolysis and oxidation conditions resulted in the presence of saturated species like ketones and final oxidation products such as CO 2 , supporting their improved combustion and emissions' reduction in the engine tests.